(1) Field of the invention
This invention relates to a robust method of fabrication used for semiconductor integrated circuit devices, and more specifically to the formation of an improved copper metal diffusion barrier layer that improves copper seed layer adhesion, in a single and dual damascene process, to fabricate reliable metal interconnects and contact vias.
(2) Description of Related Art
Related patents and relevant literature now follow as Prior Art.
U.S. Pat. No. 5,066,615 (Brady et al.) teaches a sputtering method to form TaSiN and other anti-reflection material layers. An antireflection coating for use in integrated circuit processing consists of a film of x-silicon-nitride, where x is a metal from the group consisting of titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum and tungsten. These coatings are preferably made by sputtering, with the x silicon nitride coating being made by sputtering in a nitrogen-containing atmosphere.
U.S. Pat. No. 5,913,147 (Dubin et al.) describes diffusion barriers from the group Ta, TaN, W, WN, TiW, TiN, TaSiN, TiSiN, WSiN. A method for fabricating copper-aluminum metallization utilizing the technique of electroless copper deposition is described. The method provides a self-encapsulated copper-aluminum metallization structure.
U.S. Pat. No. 5,614,437 (Choudhury) describes a method for manufacturing an ohmic contact on a semiconductor device and includes as a first step, etching a via through a non-conductive layer formed over a partially fabricated version of the semiconductor device. This step exposes a region of a device element such as a source, gate electrode, etc. Next, an ohmic contact layer including tantalum and silicon is deposited over the partially fabricated device and in the vias by sputtering in an argon atmosphere. Thereafter, and in the same processing apparatus, a barrier layer including a tantalum silicon nitride, TaSiN, is deposited over the ohmic contact layer. Then an aluminum alloy metallization layer is directly deposited on the partially fabricated device at a temperature of at least 650 C. At this deposition temperature, the metallization layer conformally fills the via, thereby producing a stable, uniform contact.
U.S. Pat. No. 5,893,752 (Zhang et al.) mentions TaN barrier layers and tantalum oxy-nitride barrier layers. A semiconductor device is described. The first conductive film is over the substrate and a second conductive film is over the first conductive film. The first conductive film includes a refractory metal and nitrogen. The first conductive film has a first portion that lies closer to the substrate and a second portion that lies further from the substrate. The nitrogen percentage for the second portion is lower than the nitrogen atomic percentage for the first portion. The second conductive film includes mostly copper. The combination of portions within the first conductive film provides a good diffusion barrier (first portion) and has good adhesion (second portion) with the second conductive film.
U.S. Pat. No. 5,913,144 (Nguyen et al.) teaches an oxygen containing plasma treatment of a TiN, TiON, TiSiN, TaSiN, TaN, TiW, TiWN, Mo, and WN and other barrier layers. The method claims improvement of adhesion of copper to the diffusion barrier material, such as TIN, in an integrated circuit substrate. The diffusion barrier is exposed to either a reactive oxygen species, or a plasma containing oxygen. A thin layer of the diffusion barrier is oxidized, typically less than 50 xc3x85, in response to exposure to the oxygen environment. CVD copper is then deposited over the oxidized diffusion barrier surface. The oxide layer improves bonding between the copper and diffusion barrier surfaces. The oxide layer permits the control of tolerances in the diffusion barrier preparation processes, and copper precursor, to be relaxed. An integrated circuit comprising an oxide layer between the diffusion barrier and the copper layer is also provided.
U.S. Pat. No. 5,712,193 (Hower et al.) describes a method of treating the surface of a metal nitride barrier layer on an integrated circuit to reduce the movement of silicon through the barrier. The metal nitride barrier (such as TiN) is exposed to a nitrogen plasma, thereby improving the barrier properties of the metal nitride barrier.
U.S. Pat. No. 5,801,098 (Fiordalice et al.) describes a TiN layer exposed to a nitrogen plasma treatment. Furthermore, a method of decreasing resistivity in an electrically conductive layer is described using a high density plasma sputtering technique to deposit the electrically conductive layer over a substrate and exposing the electrically conductive layer to an anneal in an ambient comprised of a plasma.
It is a general object of the present invention to provide an improved robust method of forming a copper metal diffusion barrier layer, in a single and dual damascene process, to fabricate reliable metal interconnects and contact vias.
For completeness provided by the present invention, is a semiconductor substrate with an insulating layer thereon. A copper metal interconnect typically is patterned within an insulating layer. In addition, a layer of interlevel dielectric (ILD) is deposited and patterned into a trench structure or xe2x80x9cgapxe2x80x9d opening. Provided can be both a single and dual damascene structure. The insulating material is typically silicon oxide compounds.
The first embodiment of the present invention is the deposition by physical vapor deposition (PVD) sputtering (reactive sputtering for nitride compounds) or chemical vapor deposition (CVD) of a copper metal diffusion barrier layer, which consists of the following materials: TaN, Ta, TiN, or WN.
Next in the process is the one of the main embodiments of the current invention, the silane treatment process of said barrier layer. Silicon doping by a silane gas plasma treatment or xe2x80x9csilane soakingxe2x80x9d is performed upon the surface of the barrier layer and the silane soaking is performed under the following conditions: plasma power from about 300 to 600 W, plasma time from about 5 to 240 sec. The silicon doping occurs first at the surface of the barrier, raising the surface concentration of silicon to high levels.
In yet another main embodiment of the current invention, is formation of regions of silated TaSi, or TaSiN, or TiSiN, or WSiN, silicon doped compounds, by the aforementioned plasma treatment or silane soaking. In addition, a heat treatment thermal annealing process is applied which drives in the silicides into barrier layer. Exact thermal annealing conditions to convert barrier metal compounds into robust amorphous diffusion barriers are summarized below. It was found that the silated silicon doped compounds exhibit better adhesion properties when combined with chemical vapor deposition (CVD) of copper seed layer. Also, silated silicon doped compound exhibit better resistance to fluorine ion attack, F-, in subsequent processing. As the first example, silated TiN barrier material, TiSiN, forms good diffusion barrier material when annealed at 600xc2x0 C. and has an amorphous structure. In a similar technique, silated TaN barrier material, TaSiN, forms a good diffusion barrier material when annealed at 900xc2x0 C. and has amorphous structure. Amorphous barrier layers prohibit the rapid grain boundary diffusion mechanism since crystal grains and associated grain boundaries are not present. Scanning electron microscope (SEM) analysis of the silated barrier layers reveal highly dense films ( greater than 99%) and regions of silicides with low silicon content.
In another embodiment of the present invention, the chemical vapor deposition (CVD) of the copper seed layer is performed upon the silated barrier layer. The chemical vapor deposited (CVD) copper seed layer exhibits improved adhesion upon the rigid high density diffusion barrier layer and the silated barrier region. In a subsequent process step, an electrochemical deposition (ECD) of copper is used to fill the trench cavity, upon the copper seed layer.
The next processing step in the building of a single or dual damascene structure is the deposition of copper upon the seed layer, by electrochemical copper deposition (ECD). The kinetics of the electrochemical copper deposition process are based on a uniform, defect-free seed layer and barrier layer with good adhesion properties. The underlying layers improve and make wider the process window for the chemical vapor deposition (CVD) of copper to fill both single and dual damascene structures.
The final processing step in building of the single and dual damascene structure is the chemical mechanical polishing (CMP) back of the excess electrochemical deposited copper metal. The copper is chem-mech polished back without dishing. The copper is polished back so that only the copper that lies in the openings is left to form single and dual inlaid structures that include via and interconnect portions. Device applications include MOSFET and CMOS devices.
This invention has been summarized above and described with reference to the preferred embodiments. Some processing details have been omitted and are understood by those skilled in the art. More details of this invention are stated in the xe2x80x9cDESCRIPTION OF THE PREFERRED EMBODIMENTSxe2x80x9d section.